SERVICE AND SPARES
6 720 804 532 (2012/09)
36
6.6
SETTING THE AIR/GAS RATIO
6.6.1
SETTING THE CO/CO
2
▶ Refer to section 5.6.1 and ensure that the gas inlet pressure is correct
before continuing.
▶ To adjust the CO/CO
2
it will be necessary to first operate the boiler at
maximum output.
1. Press and hold down the service button for more than 10 seconds
until illuminated.
The blue power indicator will pulse 5 times.
2. Turn central heating control to maximum; the boiler will then go to
maximum output.
Fig. 79 Setting the boiler
▶ Refer to table 20 and check the CO/CO
2
at maximum. If required set
the maximum CO/CO
2
via adjuster (1) on the gas valve using a 2.5mm
Allen key.
▶ Check CO is less than 200ppm.
3. Set the central heating control to minimum.
▶ The boiler will go to minimum power.
▶ Measure the CO/CO
2
and check against table 20 below.
If required set the minimum CO/CO
2
via adjuster (2) on the gas valve
until the correct measurement is set:
– Remove dust cap with flat bladed screw driver.
– Using a 4mm Allen key adjust CO
2
.
– Replace the dust cap.
▶ Check that the CO is less than 200ppm.
▶ Return to maximum and re-check the CO/CO
2
.
If correct, press the service button;
the button will cease to be illuminated and the blue power indicator
will be permanently illuminated.
▶ Re-assemble and refit boiler case.
Fig. 80 Gas valve adjustment
6.7
CLEANING THE HEAT EXCHANGER
▶ Isolate the power to the appliance and remove outer case and base
panel.
1. Refer to figure 81 and remove the clip from gas valve outlet.
2. Pull the gas outlet elbow free from the gas valve.
NOTICE:
THE SETTING OF THE GAS RATIO MUST BE
CARRIED OUT BY A COMPETENT PERSON. SETTING OF
THE GAS RATIO MUST NOT BE ATTEMPTED UNLESS
THE PERSON CARRYING OUT THE TEST IS EQUIPPED
WITH A COMBUSTION ANALYSER CONFORMING TO BS
7927 AND IS COMPETENT IN ITS USE.
The control will resume normal operation after 15
minutes or if the service button is pressed for more than
a second.
1.
2.
3.
6720643895-120.1W
o
CO/CO
2
settings for Greenstar i System
CO/CO
2
should be measured after 10 minutes.
Gas type
CO
2
max.
CO
2
min.
Natural gas 12i System
9.65%
±
0.5
8.65%
±
0.5
Natural gas 15,18 & 24i System 9.8%
±
0.5
9.2%
±
0.5
L.P.G.
11.0%
±
0.5
10.5%
±
0.5
NOTE:
When checking an existing appliance the tolerance is
±
0.5.
If checking after cleaning or component replacement or for adjustment
when the reading obtained is outside the tolerances given above, then
the tolerance is
±
0.2.
CO - less than 200 ppm (0.002 ratio)
Table 20 CO/CO
2
settings
NOTICE:
COMBUSTION TESTING
▶ Combustion testing must be carried out by a
competent person. Testing must not be attempted
unless the person carrying out the combustion check
is equipped with a Combustion Analyser conforming
to BS 7927 and is competent in its use.
NOTICE:
CO/CO
2
CHECKS
▶ If the joint between the Air/Gas manifold and heat
exchanger is disturbed sealing gasket must be
replaced.
▶ After completing the service of the appliance, the CO/
CO
2
must be checked and set to the limits shown in
“Setting the air/gas ratio” on page 36.
There is a special accessory kit available specifically
designed for cleaning the heat exchanger. If required
order 7 716 192 312.
If the plastic elbow can not be easily removed, undo the
nut to push the plastic elbow out of the fitting.
6720643895-66.1Wo
2
1
MAX
MIN
2.5 mm
4 mm